Chevrolet Repair: Digital EGR valve, egr valve, gm dealership

Question
I called the parts department at the GM dealership and they have no information on the resistance of the solenoids.  When the exhaust from the EGR goes into the plenum, does it follow a tube to the throttle body and then mixes in with the gas or does it fill up the plenum.  I have heard a lot about the passage being clogged in the intake and the plenum has to be removed to clean it out right, sometimes just cleanning behind the throttle body does it.  If I could find a diagram on how the plenum works, I could probably figure it out from there.  
Thanks

Answer
The Exhaust Gas Recirculator sends unburnt fuel or gases back to the intake via the attached pipe in the picture.
Removing the EGR itself should show the amount of carbon build up underneath.
If it's built up underneath, then it's probably built up in the tube as well.